Nuclear magnetic resonance (NMR) techniques have been used to investigate and measure material properties. Perhaps the best known application of NMR techniques is magnetic resonance imaging (MRI) that non-invasively examines a person's body. MRI can produce three dimensional volume representations that can be displayed as two dimensional images for a diagnostician. The most common NMR instruments use very large superconducting magnets that produce intense magnetic fields.
More recently, ultra-low magnetic field NMR techniques using SQUIDs have been developed. The advantage of ultra-low magnetic fields is that they can be produced by smaller magnets. In some cases, the earth's magnetic field can be used as the measurement field.
Border security, airport security, and inspections at the entrances to secured areas have become valued, yet intrusive, aspects of life. In general, less intrusive and time consuming searches are acceptable by the public. However, only detailed searches can identify many threats. X-ray techniques and chemical sniffer techniques followed by detailed searches as required have been used in many high throughput scenarios. Regardless, many threats can easily evade detection. For example, materials such as shampoo and soap are hard to distinguish from certain explosives unless the materials are individually accessed and examined. As such, systems and methods are needed that can detect hazardous materials such as explosives and explosive precursors in a high throughput and non-invasive way.